Symptomatic vertebral artery conflicts to the medulla oblongata and microsurgical treatment options: review of the literature

Abstract

Symptomatic vascular compression of the medulla oblongata causing brainstem dysfunction is extremely rare. Only a few case reports documenting the clinical condition of patients, diagnostic features and therapeutic options are available in literature. The Medline search revealed with the present cases a total of 9 reports on patients with symptomatic vertebral artery compression to the brainstem. Out of these reports the observed symptoms comprise hypertension, hemiparesis, tetraparesis, hemihypaesthesia, pyramidal tract signs, central sleep apnea and vertigo. Moreover an overview of the various suggested and published microsurgical procedures is given. Based on the literature search basically 4 different microsurgical strategies are documented, the vessel mobilization, the vessel section with posterior fossa decompression, the autologous material inlay with posterior fossa decompression and the lateral vessel retraction assisted with Gore-Tex. Vascular compression causing brainstem deficits are particularly unusual in the young population. Two illustrative cases of young men with a symptomatic vertebral artery brainstem conflict who were treated microsurgically with vascular decompression are additionally discussed in the present article. The history, diagnostic features, microsurgical treatment and outcome of these patients are described in detail. As a conclusion these cases demonstrated that careful examination can serve to determine the diagnosis even in the young population microsurgical treated successfully. In conclusion the present review tries to provide an overview of the existent data on the variety of clinical, radiological and surgical features in patients with symptomatic vascular brainstem compression.

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Comments

Ernst Delwel, Rotterdam, The Netherlands

The concept of hypertension caused by symptomatic compression of the medulla oblongata is still subject of controversy and scepticism.

To the reference list of the authors I would like to add and quote an early article by Jannetta, the pioneer on neurovascular compression syndromes [1]. He explored the cerebellopontine angle in patients who underwent a microvascular decompression (MVD) for a trigeminal neuralgia (TN), a hemifacial spasm (HFS) or eigth nerve dysfunction. All these 28 patients had essential hypertension of which 20 were females and 8 were males, ranging 31-74 years of age. In all cases he found a vascular compression on the left ventral side of the medulla oblongata, mostly caused by an elongated vertebral artery or a PICA loop.

In 1985 Jannetta [ref. 7 in the article of the authors] demonstrated a pulsatile compression of the left rostroventrolateral medulla (RVLM) in 51 of 53 patients undergoing MVD for TN or HFS and with essential hypertension. MVD of the RVLM was performed in 42 patients and was successful in 36 patients, leaving 31 patients normotensive.

The authors show some relatively unique findings, namely a vascular compression on the right RVLM in case 1 and the young age of both patients. The authors use the suture sling method first described by Spetzler and Koos [2] and Bejjani and Sekhar [3] for decompression of the medulla by separation of the offending vessel. This method is considered the most reliable and long-lasting in effect.

The question still remaining is: which patients with essential hypertension are good candidates for an MVD procedure? If we consider that 10% of the American population has hypertension and annually, 1.6 million of Americans are newly diagnosed with hypertension, of which 90% has essential hypertension, only a small fraction of them could, for practical reasons, ever undergo an MVD. If we extrapolate these facts to the whole world, there simply are not enough neurosurgeons to accomplish this tremendous effort.

Levy et all [4] state that refractory essential hypertension with a proven neurovascular conflict on MRI is an indication for an MVD procedure. The patient should have used at least three oral anti- hypertensive drugs without success, before this diagnosis can be made.

The authors don not fully convince me with their results. In both cases, the preoperative blood pressure was not extremely high with medication. In case 1, the blood pressure postoperatively was still mildly elevated for a 24 year old man, 140/90, although without medication.

I agree with the comment of Heros on the article of Levy et al [5] A large prospective study is needed with a control group of patients with (essential refractory) hypertension who will be determined not to have a neurovascular compression, to serve as a placebo group.

Nevertheless, the authors are to be complimented with their well documented study, their good and uneventful surgery and their demonstration of the operative effect by MRI scan. They have certainly added some pieces of the jigsaw puzzle named “the enigma of essential hypertension caused by neurovascular compression of the rostroventrolateral medulla”.

The authors of this review, which is of high quality and easy to read, have focused on the role of vertebral artery conflict to the medulla oblongata, it’s related symptoms and treatment options aiming at searching for consensus and guidelines for this rare condition. This review, that should be mandatory reading for all residents in neurosurgery, also includes interesting comments concerning possible biological mechanisms involved in symptoms related to a neurovascular conflict, which is a complex area. The paper sets not only focus on the role of microsurgery but also the importance of preoperative evaluation with interesting aspects concerning risk-benefit-analyses. The latter is for natural reason difficult since the literature is limited to a hand full of case reports describing few patients. Prediction of outcome prior to intervention is for the same reason difficult; however in this review the authors summarize relevant data not only from the literature but also from their own wide experience in the field, including long-term follow ups. The authors describe different surgical procedures on how to handle this condition, however focusing on the “lateral vessel retraction assisted with Goretex” that clearly works well in their hands. Retracting a tortuous segment of the vertebral artery is a hazardous and difficult procedure also in the hands of experienced neurosurgeons. The procedure is descried in detail in this review, in particular with respect on how to protect the perforators. These comments will probably be appreciated by any readers of this article involved with microvascular decompression procedures. In summary, the authors have put a lot of effort in summarising the literature of this complex area and hopefully we will read more from this group in the future.